Selective radio receiver



April 28, WEE. M OSNOS E 2,638,872

SELECTIVE RADIO RECEIVER Filed Nov. 17, 1931 INVENTOR MEND/EL OSNOS BY ATTORNEY Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE Mendel Osnos, Berlin,

Germany,

assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application November 17, 1931, Serial No. 575,562 In Germany March 4, 1931 8 Claims.

The present invention is a further improvement upon a prior arangement disclosed in my German application 38,341 VIIIa/21a4. According to the latter piezo-electric crystals are used as a means to stop or reject undesirable waves, said crystals being tuned to these waves. So far as the desired waves are concerned, the said crystals operate as capacitive reactances so that it is necessary as a general rule to neutralize the said reactance for the desired waves by means of a suitable inductance coil connected in series with the crystal.

According to this invention the said inductance coil is rendered wholly, or partly, dispensable by that the crystals serving as rejector, or stopper, means are included in a circuit having an inherently very high resistance so that the capacitive reactance of the crystal has a negligible low influence, or where the inductive reactance already exists which neutralizes the capacitive reactance of the crystal wholly, or in part. Circuits of this kind, for instance, are grid circuits of different radio frequency receiver stages. It is particularly advantageous to insert the stopper, or rejector, crystal in the grid circuit of the audion stage.

The novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims, the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indicated diagramatically one circuit arangement whereby my invention may be carried into effect.

One embodiment of the principle underlying the invention is diagrammatically illustrated in the accompanying drawing, where a is an audion, or detector, and b is an audio frequency amplifier comprised in the receiver set fed from the aerial through a transformer comprising the primary winding I and the secondary winding 2. The secondary winding 2 is shunted by a variable capacity 3. The anode of the tube a is connected to the cathode end of secondary winding 2 by means of a coupling coil 4 and a variable condenser for the purpose of producing controllable regeneration. K denotes, further, the crystal connected in the grid circuit of the audion tube a and being tuned to an undesired wave. For instance, if in long distance reception the wave of 120 meters of a local transmitter station has proved troublesome, then the crystal 7c is so chosen that its natural period corresponds to a wave of 120 meters. The audion, or detector, is

of the regenerative type, and the crystal K is connected between the low radio frequency potential side of the tunable input circuit of tube a and the grid of the latter. The high radio frequency potential side of the detector input circuit is connected to the negative leg of the oathode of tube a. The usual grid leak is connected between the grid and the cathode. The capacitative reactance of the crystal K is utilized as the usual leaky grid condenser of the detector tube a.

While I have indicated and described one arrangement for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organization shown and described, but that many modifications may be made without departing from the scope of my invention as set forth in the appended claims.

What I claim is:

1. In a radio receiver, a tube including at least a cathode, an anode and a grid, an output load network connected between the anode and. cathode, a resonant radio frequency input circuit, a tuning reactance in the input circuit for resonating it to a desired signal frequency, a piezoelectric element connecting the said grid to one side of the input circuit, and a connection between the tube cathode and. the opposite side of the input circuit, said element having a natural period equal to the frequency of an undesired signal.

2. In a radio receiver, a tube including at least a cathode, an anode and a grid, an output load network connected between the anode and cathode, a resonant radio frequency input circuit, a tuning reactance in the input circuit for resonating it to a desired signal frequency, a peizoelectric element connecting the said grid to the low radio frequency potential side of the input circuit, and a connection between the tube cathode and the opposite side of the input circuit, said element having a natural period equal to the frequency of an undesired signal.

3. In a radio receiver, a tube including at least a cathode, an anode and a grid, an output load network connected between the anode and cathode, a resonant radio frequency input circuit, a tuning reactance in the input circuit for resonating it to a desired signal frequency, a piezo-electric element connecting the said grid to one side of the input circuit, and a connection between the tube cathode and the opposite side of the input circuit, said element having a natural period equal to the frequency of an undesired side of the input circuit, and a connection be-' tween the tube cathode and the opposite side of the input circuit, said element having a natural period equal to the frequency of an undesired signal, said load network comprising an audio frequency amplifier, and said tube providing a detector.

5. In aradio receiver, a tube including at least a cathode, an anode and a grid, an output load network connected between the anode and cathode, a resonant radio frequency input circuit, a

tuning reactance in the input circuit for reso-' nating it to a desired signal frequency, a piezoelectric element connecting the said grid to one side of the input circuit, and aconnection between the tube cathode and the opposite side of the input circuit, said element having a natural period equal to the frequency of an undesired signal, said element having a capacitative reactance acting as a leaky grid condenser to render the tube a detector, agrid leak resistor connected between the grid and cathode of the tube, and said network including an audio frequency amplifier. t i 6. In a radio receiver an electronic tube having at least an anode, a cathode and a gridelectrode, a tuned circuit comprising an inductance coil and a tuning condenser connected so as to form a closed circuit, a source of signalling energy coupled to said inductance coil so that one side of said coil may be considered as a low potential sideto the signal energy while the other side may be considered as the high potential side to the signalling energy, a connection between the oathode of the tube and the high potential side of the inductance coil, a connection between the grid electrode of the tube and the low potential side of the coil said last named connection including a resonator device having a natural period equal to a frequency of an undesired signal, an output circuit for said tube including a'coupling element and an output load'network connected to said coupling element. i

'7. In a radio receiver a detector tube having at least an anode, a cathode and a grid electrode, a tuned circuit including an inductance coil and a shunted tuning condenser, a source of signalling energy coupled to said inductance coil in such a way that one side of such a coil may be considered as the low potential side as regards the signal energy while the other side of the coil may be considered as the high potential side, a connection between the cathode of the tube and the high potential side of the coil, a connection between the grid electrode of the tube and the low potential side of the coil said last named connection including a resonator device having a substantial capacitive reactance, said resonator device having a natural period equal to a frequency of an undesired signal, an impedance element connected between said grid electrode and cathode, the capacitive reactance of the resonator device and said impedance element acting together to give said electronic tube a detector characteristic, an output circuit for said tube including a coupling element and an output load network connected to said coupling element.

8. In a regenerative detector circuit an electronic tube provided with an anode, a cathode and at least one grid electrode, a tuned circuit comprising an inductance coil shunted by a tuning condenser, a source of signalling energy coupled to said inductance coil said inductance coil being arranged with respect to the source of signalling energy so that one side of the coil may be considered as a low potential side with respect to the signalling energy while the other side may be considered as the high potential side, aconnection between the cathode of the tube and the high potential side of theinductance coil, means including a resonator device, having substantial capacitive reactance for connecting the grid electrode of the tube to the low potential side of the coil, said resonator device having a natural period equal to the frequency of an undesired signal whereby said device acts as a rejector, an impedance element connected between the grid electrode and the cathode said impedance deviceacting in conjunction with the capacitive reactance of the resonator device to give the tube a detector characteristic, a connection between the anode of the tube and the cathode including a variable capacity device and an inductor element in series, said inductor element being coupled to the said inductance coil said last named connection being arranged so as to produce controlled regeneration, an output circuit for said tube including a coupling element and a utilizing network connected to said coupling element.

MENDEL OSNOS. 

